Display MoreOutput of modetest and kodi log may be useful (you should be able to ssh in).
It may also be of interest to switch to the fkms driver.
You'll need to edit /flash/distroconfig.txt. Change:
dtoverlay=vc4-kms-v3d,cma-512
to
dtoverlay=vc4-fkms-v3d,cma-512
i found this thread because i was having issues getting my raspberry pi 4 model b to connect to the rear seat entertainment fire tv screens in a 2023 jeep wagoneer, i would get the rainbow screen and then a black screen, i made this simple fkms driver adjustment and it immediately worked - now i’ve got to move on and figure out how to program a custom output resolution to match these screens so there’s no scaling, but at least we’ve got signal now! thank you